Inhibition of soluble guanylate cyclase by bovine serum albumin.

Bovine serum albumin (BSA) and to a lesser extent beta-lactoglobulin produced concentration-dependent inhibition of the guanylate cyclase activity in supernatant fraction and partially purified enzyme (PPE) prepared from rat lung homogenates. Ovalbumin had little effect. Some activity was lost when PPE was applied to a BSA-agarose column, however the loss disappeared when the enzyme reaction mixture contained Lubrol PX. Also, BSA no longer inhibited PPE after BSA-agarose treatment. BSA inhibition of PPE was not apparent when activity was maximally stimulated by arachidonate. These data were interpreted as indicating that the enzyme had bound to it an amphiphilic activator, possibly a fatty acid, the removal of which by BSA decreased activity.